One problem with remediation programs for problem aggression may be that they are begun too late, after aggressive styles have become highly stable elements of personality, resistent to change. This research attempts to lay the groundwork for earlier prevention and intervention by studying the early origins of highly aggressive behavior, and the factors that contribute to the development of such patterns. Children are studied beginning as early as one year of age, and followed-up three years later. Two main findings have emerged: (1) There is evidence for an aggressive syndrome in young boys, marked by sensitivity to environmental stress, high intensity of agression, labile emotions, and high stability of aggression over time and in multiple settings. (2) Anger or conflict between adults acts as a powerful instigator of aggression in young children, increasing the incidence and hostility of aggression. Repeated exposure to background anger increases aggressive reactions.